Historically, railroad rails have been made from carbon steels, having a hardness of about 270 on the Brinell hardness number scale. However, over the years, as loads became heavier and traffic volumes higher, railway companies began to demand a harder rail, having better wear characteristics. Steel companies responded to this demand in the 1960's by producing a high alloy rail, having a steel composition which included about 1.4% chromium, and an average hardness of about 335 Brinell. Subsequently, other high alloy rails, having chemical compositions which included alloys such as molybdenum and vanadium in addition to chromium, were developed. These high alloy rails, however, proved to be expensive to produce and difficult to weld. Moreover, brittle martensite tends to be formed in the welds of these high alloy rails, which can cause the weld to break catastrophically.
More recently, a number of methods have been developed for the production of a premium rail composed of fine pearlite and having an average hardness of 370 Brinell. Off-line head hardening methods, involving re-heating rolled rail sections made from carbon steel, were introduced, but these methods are costly and suffer from low production rates. These disadvantages are overcome by in-line accelerated cooling processes for treating carbon rails, such as those described in U.S. Pat. No. 4,486,248 (Ackert et al) granted to the Algoma Steel Corporation, Limited, and U.S. Pat. No. 4,668,308 (Economopoulos et al), granted to Centre de Researches Metallurgiques and Metallurgique et Miniere du Rodange-Athus et al. The Algoma Steel process results in a relatively hard carbon steel rail, having an average head hardness of 360 Brinell, which is easier to weld, and less expensive to manufacture, than high alloy rails or off-line heat treated rails. However, hardened carbon rails, whether produced by an on-line or an off-line process, require the end user to perform special welding techniques, in order to avoid soft welds which wear prematurely. Not all railway companies have the inclination or expertise to employ special welding techniques on a consistent basis. As a result, there remains a need for an inexpensive premium rail having desirable welding properties.